Method and apparatus for analyzing articles



March 16, 1965 FIG.

HF SIGNAL GENERATOR L. G. SIMJIAN METHOD AND APPARATUS FOR ANALYZING ARTICLES Filed 001;. 26, 1960 FIG. 2

HF SIGNAL GENERATOR INVENTOR. LUTHER Gv SIMJIAN AGENT United States Patent 3,173,291 METHOD AND APPARATUS FOR ANALYZING ARTICLES Luther G. Simjian, Greenwich, Conn., assignor to Universal Match Corporation, St. Louis, Mo., a corporation of Delaware Filed Oct. 26, 1960, Ser. No. 65,133 16 Claims. (Cl. 73'67.1)

This invention concerns a method and apparatus for analyzing and determining the character of an article by radiant energy and has reference more particularly to a method for determining the character of a document by the use of acoustic energy.

In a specific sense, the present invention is useful for establishing the type or denomination of an imprinted document, such as money bills, using acoustic energy to sense the presence or absence of a predetermined printed pattern.

It is well known that when making acoustic measurements or applying an acoustic signal to a body which is to be explored, it is necessary to use a thin film of liquid, particularly oil, between the probe which radiates the energy and the body being investigated in order to obtain good coupling of acoustic energy. Otherwise air which is present at the interface between the probe and the body causes severe attenuation of acoustic energy.

It is known that genuine money bills issued by the United States Government are printed with a definite pattern of green ink which apparently never completely dries. In fact, this property of the ink is one of the salient characteristics which distinguishes a genuine bill from a counterfeit one. Regardless of the age of the bill, when rubbing a genuine bill against a white sheet of paper a green smear is obtained. Since the ink or dye remains in some type of suspension, the presence or absence of a printed pattern can readily be established by applying an acoustic energy probe to the document, whereby a first type of signal is obtained when the inked pattern is present and a second type of signal when the printed pattern is absent. These differences are caused by the varying degrees of coupling between the acoustic probe and the paper bill due to the ink suspension acting as a coupling medium.

Moreover, since the various denominations are printed with different patterns and differing locations within the over-all configuration of the document, it is possible to analyze the type and character of a document by selecting certain spots on a document and comparing the acoustic properties of these spots with predetermined or standardized values. Also, counterfeit documents may readily be detected since ordinary printing ink dries rapidly so that the degree of coupling at all places will substantially equal the value obtained when a printed pattern is absent. A genuine money bill where the printing ink remains somewhat liquid will show however, values which differ along the surface of the bill as areas with printed information alternate with blank areas.

In its practical embodiment, it will be advantageous to make a plurality of measurements using acoutic energy at several predetermined locations of the money bill and compare the individual measurements with preselected or standardized values. In this manner, it is possible to compare an unknown document with standardized values, determine whether the document falls within prescribed categories or denominations, and accept or reject the document.

One of the objects of this invention therefore, is the provision of a method for analyzing articles using radiant energy.

Another object of this invention is the provision of a method and apparatus for analyzing printed documents, printed documents.

Another object of this invention is a method and apparatus for determining the character and denomination of a printed article, such as a money bill, by measuring the acoustic coupling between a probe and the document.

A further and other object of this invention is the provision of a method and apparatus for sorting, accepting and/or rejecting documents using acoustic energy by determining the presence or absence of a predetermined printed pattern on the document under investigation.

A still further and other object of this invention is a method and apparatus for analyzing pirnted documents, accepting documents which are provided with a special type of printing ink, and sorting documents whose printed pattern falls within definite categories.

Other and still further objects of this invention will be apparent from the following description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a schematic diagram explaining the principle of the present invention;

FIGURE 2 is a schematic diagram of a circuit which may be used for investigating a single location on the article under investigation;

FIGURE 3 is a diagram of an improved circuit showing sequential investigation of a plurality of locations on a document under investigation;

FIGURE 4 is a schematic circuit diagram showing a variation of the arrangement shown in FIGURE 3;

FIGURE 5 is a circuit diagram of a further arrangement for investigating an article, and

FIGURE 6 is a schematic diagram of a still further arrangement.

Referring now to the figures and FIGURE 1 in particular, numeral 11 refers to an article under investigation and in this particular instance, to a currency note or paper bill as printed by the United States Government. As has been explained hereinbefore, the document is imprinted with a predetermined pattern of graphic representations using green metallic ink or dye which does not completely dry. The printing pattern differs from denomination to denomination and it is well understood that a $1.00 bill has a pattern which is different from a $5.00 or $10.00 bill. Not only is the pictorial representation in itself different, but the location of the printed pattern within the printed frame varies considerably from denomination to denomination. It will be apparent therefore, that money bills can be sorted and investigated by checking the presence or absence of printed matter at various locations. Numeral 12 in FIG- URE 1 refers to an electronic high frequency signal generator, preferably in the ultrasonic range, above 16,000 cycles per second, in order to maintain the entire equipment at a convenient size.

Numeral :13 refers to an acoustic probe, preferably a transducer which receives the high frequency signal as its input and generates an acoustic signal as output. Such transducers are usually made of quartz, barium titanate, ferrite, or nickel material as is well known in the art of ultrasonic testing. The transducer or probe is in contact with document 11, the latter being supported on a roller or platen 14 made of sound absorbing material, for instance rubber.

When there is a good coupling between the probe and the document 11 due to the presence of an ink suspension, 2. current of larger magnitude will flow through the current sensing element 18 which is connected serially be.- tween the generator 12 and the probe 13 than when there is a lack of satisfactory coupling between the probe and thedocument. This phenomenon is well known since in the first case there is what is usually called a good impedance match while in the second case there is a lack of proper impedance matching. The current sensed by element 18, for instance, a transformer or a resistance, is amplified by an AC. amplifier and rendered visible at meter 16 which thus displays a value indicative of the current flowing to the probe and hence of the degree of coupling between the article 11 and probe 13. A low reading on meter 16 indicates a lack of good coupling or absence of an ink suspension, Whereas a higher value will indicate a larger amount of current flow, good coupling and hence, presence of an ink suspension.

The circuit per. FIGURE 2 includes a means for automatically comparing the measured value with a standard. The high frequency signal generator 12 is connected in series with one pole of an oscillating chopper 21 to the ultrasonic probe 13 which is in contact with the document 11 and supported by platen 14. The other pole of the chopper is connected to an impedance standard 22 comprising the combination of a capacitor, a reactor and a resistor. Assuming that the impedance between probe 13, document 11 and platen 14 equals the impedance of the impedance standard 22, then as the chopper switches alternately from impedance standard 22 to probe 13, there will be no difference signal to amplifier 15 and to meter 24'so that relay coil 23 remains ole-energized. If, however, the impedance between probe 13, document 11 and platen 14 varies in magnitude from the impedance of the impedance standard 22, then there will be a difference sig nal developed by the amplifier 15 and if of sufiicient magnitude will cause energizing of relay 23. The contacts associated with the coil are connected to a control circuit (not shown) to either accept or reject the particular document. It will be understood that document 11 must be positioned accurately with respect to probe 13, a feature which readily is accomplished by well-known positioning and indexing means.

FIGURE 3 refers to a further embodiment wherein sequentially a plurality of locations on a document is investigated by means of the technique described hereinbefore. Document 11 now is positioned on an indexing table and moves in stepwise fashion relative to stationary probe 13 and platen 14 as indicated by the arrow 31. For each location to be investigated along the document there is provided an impedance standard 22A, 22B, 22C, 22D, etc. and an associated relay coil 23A, 23B, 23C and 23]). By means of a commutator, stepping switch or other switching device 21A, one of the impedances is connected at any one time to the respective relay coil and the advance of the switching device is synchronized with the motion of the document 11. As shown, the document is positioned between probe 13 and platen 14 for investigating a particular spot on the document and chopper 21 switches between probe 13 and impedance standard 22D. If amplifier 15 develops substantially no difference signal then theimpedance of the impedance standard 221) equals the impedance found between the probe, document and platen. In the event a difference signal of sufficient magnitude is present, relay 23D becomes energized. In the ensuing cycle document 11 is advanced by a predetermined distance toward the right, in the direction of arrow 31, and impedance standard 22C and relay 23C will be connected in the circuit. This procedure is repeated for the other locations to be investigated and the selective energization or nonenergization of the relay coils will then be indicative of the character or denomination of the document 11.

The circuit shown in FIGURE 4 is similar to the arrangement described in FIGURE 3 except that the article or document 11 which is to be investigated is held stationary. There is provided a plurality of probes 13A, 13B, 13C, and 13D and a corresponding number of op posing sound absorbing platens 14A through 14D. In a similar fashion there is arranged a plurality of impedance standards 22A through 22D. When the probe is located at a pr'edetermined spot on a valid document, the

circuit has an impedance which equals the impedance of a corresponding impedance standard 22A which is selected to have this value. As shown in FIGURE 4, by means of a commutator or stepping switch arrangement 21B, probe 13A and corresponding impedance 22A are alternately switched by means of chopper 21 to the amplifier 15. If the amplifier develops a signal of sumcient magnitude, reject relay 23 will be energized. After a sufficient length of time, usually a fraction of a second, the switching arrangement advances by one step to connect probe 133 and the impedance standard 22B to the ampli fier circuit. Shortly thereafter, the same procedure is repeated for the remaining locations which are to be tested.

FIGURE 5 illustrates the circuit whereinthe acoustic signal transmitted through the document is sensed. Document 11 is in contact with and interposed between a set of acoustic probes, numerals 51 and 52. High frequency generator 12 applies an electrical signal to probe 51, the acoustic signal from there being transmitted through document 11 to transducer 52 which converts the acoustic signal back to an electrical signal, thereby acting as a receiver. The electrical signal then is amplified by an amplifier 53 and applied to a meter type relay 54. This meter type relay incorporates relay contacts and is commerciaily available from The Assembly Products Corp, Chesterland, Ohio. When the indicating needle 55 deflects to a preset contact 56, a circuit is established which may be used for accepting or rejecting the document. This circuit is similar to the circuits described heretofore except that the degree of coupling on two sides of the document is investigated and the transmitted signal itself is amplified. The setting of contact 56 is'analagous to the provision of a standardized impedance value.

As has been described heretofore, in the preferred arrangement acoustic energy in the ultrasonic frequency range is used and in this particular application it is believed that frequencies in the order of 20 kc. or higher will result in an arrangement whereby the transducers are of acceptable size and the arrangement is sufficiently sensitive to provide meaningful values. In fact, the higher the frequency, the smaller the size of the transducers, and for this reason alone it will be desirable to operate the entire device at frequencies of 60 kc. or more, thus per- V mitting the use of small quartz transducer elements instead of nickel or ferrite materials commonly employed at the low frequency range.

Instead of measuring the transmitted acoustic signal as shown in FIGURE 5, it is also possible to measure the degree of coupling also by measuring the reflected signal. This arrangement is substantially equivalent to the circuits usedin thickness gauging of metals and other substances where an acoustic signal is sent into the article to be investigated and a reflected signal is measured. In this method, the transducer probe applied to one side of the metal is used alternately as a transmitter or as receiver by means of an electronic switching circuit, see for example US. Patent 2,803,129, FIGURE 4. The supporting platen may be changed to a metallic plate in order to provide awell defined return signal. This arrangement is more clearly depicted in FIGURE 6 wherein a predetermined location of document 11 is disposed between the acoustic:

probe or transducer 13 and a metallic support'plate 61.

The acoustic probe is energized from a generator 62 of acoustic energy substantially as shown in Patent No. 2,431,233 issued to W. S. Erwin, dated November 18, 1947 or to Simjian, Patent No. 2,763,153, dated September 18, 1956. A cathode ray oscilloscope 63 is connected to show the initiation of a pulse signal and a return echo, the oscilloscope being shown in the patent to Simjian supra as well as in the patent to Rassweiler et al., No. 2,431,234. Upon sending a signal from transducer 13 toward the support plate 61 a first spike 64 is visible on the cathode ray tube of the oscilloscope. A reflection pulse visible as spike 66 is obtained a brief period thereafter depending on the thickness of the various materials and the characteristics of the support plate. If the transducer 13 is in contact with a document area which is not imprinted with an ink suspension, the second pulse manifests itself as a spike of lower amplitude, indicated by dashed lines 65, the lower amplitude resulting from energy losses in cou pling between the probe and the document surface. The amplitude of the secod spike therefore is a measure of the degree of coupling between the transducer 13 and the particular document area.

While there have been described certain embodiments of the present invention it will be apparent to those skilled in the art that various changes and modifications may be made therein without deviating from the concept and spirit of the present invention, which shall be limited only by the scope of the appended claims.

What is claimed is:

1. A method for analyzing a document having a selectively applied coating which coating causes differences in acoustic coupling between a probe and said document, comprising the steps of: applying a probe radiating an acoustic signal to said document at a predetermined location of said document and measuring the acoustic signal while the probe is in contact with said document whereby the presence of said coating at said location manifests itself as an acoustic signal of different magnitude than the signal obtained in the absence of said coating.

2. A method for analyzing an imprinted document which imprinting causes differences in acoustic coupling between a probe and said document, comprising the steps of: applying a probe radiating an acoustic signal to said document at a predetermined location of said document and measuring the acoustic signal while the probe is in contact with said document whereby the presence of imprinting at said location manifests itself as an acoustic signal of different magnitude than the signal obtained in the absence of said imprinting.

3. A method for analyzing an imprinted document which imprinting causes differences in acoustic coupling between a probe and said document, comprising the steps of: applying a probe radiating an acoustic signal to said document at predetermined locations of said document and measuring the acoustic signal while the probe is in contact with said document whereby the presence of imprinting at said locations manifests itself as an acoustic signal of different magnitude than the signal obtained in the absence of imprinting at the respective locations.

4. A method for analyzing an imprinted document which imprinting causes differences in acoustic coupling between a probe and said document, comprising the steps of: sequentially applying a probe radiating an acoustic signal to said document at predetermined locations of said document and measuring the acoustic signal while the probe is in contact with said document whereby the presence of imprinting at said locations manifests itself as an acoustic signal of different magnitude than the signal ob tained in the absence of imprinting at the respective locations.

5. A method for analyzing an imprinted document which imprinting causes differences in acoustic coupling between a probe and said document, comprising the steps of: applying a probe radiating an acoustic signal to said document at a predetermined location of said document,

measuring the acoustic signal while the probe is in contact tact with said document whereby the presence of imprint ing at said location manifests itself as a signal of different magnitude than the signal obtained in the absence of imprinting, comparing the resulting signal with a signal of predetermined value, and then repeating these steps at other locations of the same document.

7. A method as set forth in claim 5 wherein the acoustic energy is in the ultrasonic frequency range.

8. A method for analyzing an imprinted document which imprinting causes differences in coupling between a robe and said document, comprising the steps of: applying a probe radiating an acoustic signal to said document at a predetermined location of said document, measuring the acoustic signal transmitted from the probe through the document while the probe is in contact with said document whereby the presence of imprinting at said location manifests itself as a signal of greater magnitude than the signal obtained in the absence of imprinting, and comparing the transmitted signal with a signal of predetermined value to establish the presence or absence of imprinted material on said document.

9. A method for analyzing an imprinted document which imprinting causes diiferences in coupling between a probe and said document, comprising the steps of: applying a probe radiating an acoustic signal to said document at a predetermined location of said document, measuring the acoustic signal reflected while the probe is in contact with said document whereby the presence of imprinting at said location manifests itself as a signal of different magnitude than the signal obtained in the absence of imprinting, and comparing the reflected signal with a signal of predetermined value to establish the presence or absence of imprinted material on said document.

10. A method for analyzing an imprinted document which imprinting causes differences in coupling between a probe and said document, comprising the steps of: interposing a predetermined location of said document between a set of acoustic transducers; radiating acoustic energy from one transducer to the other, and measuring the acoustic signal transmitted through the document while at least one of said transducers is in contact with said document, whereby the presence of imprinting at said location manifests itself as a signal of different magitude than the signal obtained in the absence of imprinting, and comparing the transmitted signal with a signal of predetermined value to establish the presence or absence of imprinted material on at least one side of said document at the particular location.

11. An apparatus for determining the character of a document which is imprinted at selected locations thereof with graphic representations whereby the material used for imprinting is of such nature as to cause differences in the acoustic coupling between a transducer and the document when comparing such coupling of an imprinted document portion with that of a non-imprinted portion, said apparatus comprising: a transducer in physical contact with the document to be analyzed at a predetermined location of the document; a standardized impedance network; a source of electrical energy operably associated with said network and said transducer for causing said transducer to radiate acoustic energy toward the predetermined location of the document; switching means connected to and alternately energizing said transducer and said impedance network from said source when said transducer is in contact with said location, and further circuit intelligence means connected in signal receiving relationship to the switching means for receiving a signal produced when the transducer and impedance network are energized in an alternate manner, whereby the value of said signal is responsive to the presence or absence of printed information at said location.

12. An apparatus as set forth in claim 11 which said acoustic energy is in the ultrasonic frequency range.

13. An apparatus for determining the character of a document which is imprinted at selected locations thereof with graphic representations whereby the material used for imprinting is of such nature as to cause differences in the acoustic coupling between a transducer and the document when comparing such coupling of an imprinted document portion with that of a non-imprinted portion, said apparatus comprising: a transducer selectively in physical contact with predetermined locations of the document to be analyzed; a plurality of standardized impedance networks; a source of electrical energy operably associated with said networks and said transducer for energizing said networks and causing said transducer to radiate acoustic energy selectively to said predetermined locations; switching means connected to and alternately coupling said source to said transducer in contact with a predetermined location and to an impedance network selected from said plurality; further circuit intelligence means connected in signal receiving relationship to the switching means for receiving and amplifying any difference signal produced when the transducer and impedance network are energized in an alternate manner, whereby the value of said signal is responsive to the degree of coupling between said transducer and document and hence indicative of the presence or absence of printed information at said location, and means for subsequently coupling the source by means of said switching means to another impedance network selected from said plurality and radiating energy to a new predetermined location of the same document.

14. An apparatus for determining the character of a. document which is imprinted at selected locations thereof with graphic representations whereby the material used for imprinting is of such nature as to cause ditlerences in the degree of acoustic coupling between a transducer and the document when comparing such coupling of an imprinted document portion with that of a non-imprinted portion, said apparatus comprising: a plurality of transducers in physical contact with respective predetermined locations of the document to be analyzed; a plurality of standardized impedance networks, one network being associated with each transducer; a source of electrical en-- ergy operably associated with said networks and said transducers for causing said transducers to radiate acoustic energy to said predetermined locations; switching means connected to said source and alternately energizing one of said transducers and the associated impedance network; circuit intelligence means connected in signal receiving relationship to the switching means for receiving and amplifying the signal produced when the respective transducer and impedance network are energized in an alternate manner whereby the magnitude of the signal is indicative of the degree of coupling and therefore responsive to the presence or absence of imprinted information at said predetermined locations, and further circuit means connected for actuation in response to said signal whereby to cause classfication of said document.

15. An apparatus for determining the character of a document which bears imprinting at different locations thereon, the material used for the imprinting being of such nature as to cause a difference in the degree of acoustic coupling and, thereby, the acoustic energy flow between the document and an acoustic transducer applied thereto at a location bearing imprinting and at a location lacking imprinting, the presence or the absence of imprinting at each predetermined location being indicative of the character of the document, comprising:

a first acoustic transducer disposed in physical contact with'a document of the type described at a predetermined location thereof;

a source of electrical energy coupled to said transducer for causing said transducer to radiate acoustic energy into the document through such imprinting as is borne at the predetermined location;

a second acoustic transducer disposed to receive said acoustic energy passing through the document from said first transducer;

circuit means coupled to said second transducer for comparing the acoustic energy received by said second transducer, and, thereby, the acoustic coupling, with a predetermined value, whereby to discover the presence or the absence of imprinting at the predetermined location of the document; and

means causing said apparatus to pass acoustic energy through an additional predetermined location on the document and to compare the energy flow, and, thereby, the acoustic coupling, with a predetermined value, whereby to discover the presence or the abence of imprinting at the additional predetermined location of the document.

16. An apparatus for determining the character of a document which bears imprinting at difierent locations thereon, the material being used for the imprinting being of such nature as to cause a difference in the degree of acoustic coupling, and, thereby, the acoustic energy flow between the document and an acoustic transducer applied thereto at a location bearing imprinting and at a location lacking imprinting, the presence or the absence of imprinting at each predetermined location of the document being indicative of the character of: the document, comprising:

an acoustic transducer disposed in physical contact with a document of the type described at a predetermined location thereof;

a source of electrical energy coupled to said transducer for causing said transducer to radiate acoustic energy into the document through such imprinting as is borne at the predetermined location;

circuit means coupled to said transducer for comparing the energy flow between said transducer and the document and, thereby, the acoustic coupling, with a predetermined value, whereby to discover the presence or the absence of imprinting at the predeterminedlocation of the document; and

means causing said apparatus to pass acoustic energy through an additional predetermined location on the document and to compare the energy flow with a predetermined value, and, thereby, the acoustic coupling, whereby to discover the presence or the absence of imprinting at the additional predetermined location of the document.

References Cited in the file of this patent UNITED STATES PATENTS 2,552,156 De France May 8, 1951 2,667,063 Cunningham Jan. 26, 1954 2,711,646 Mendousse June 28, 1955 2,782,632 Klein et a1. Feb. 1, 1957 2,803,129 Bradfield Aug. 20, 1957 2,834,236 Pardue et al May 13, 1958 2,837,914 Caldwell June 10, 1958 2,903,886 Renaut Sept; 15, 1959 2,932,818 Lubkin Apr. 12, 1960 2,986,227 Fry May 30, 1961 

1. A METHOD FOR ANALYZING A DOCUMENT HAVING A SELECTIVELY APPLIED COATING WHICH COATING CAUSES DIFFERENCES IN ACOUSTIC COUPLING BETWEEN A PROBE AND SAID DOCUMENT, COMPRISING THE STEPS OF : APPLYING A PROBE RADIATING AN ACOUSTIC SIGNAL TO SAID DOCUMENT AT A PREDETERMINED LOCATION OF SAID DOCUMENT AND MEASURING THE ACOUSTIC SIGNAL WHILE THE PROBE IS IN CONTACT WITH SAID DOCUMENT WHEREBY THE PRESENCE OF SAID COATING AT SAID LOCATION MANIFESTS ITSELF AS AN ACOUSTIC SIGNAL OF DIFFERENT MAGNITUDE THAN THE SIGNAL OBTAINED IN THE ABSENCE OF SAID COATING. 